Superior-and-inferior-limb blood-pressure index measuring apparatus and inferior-limb blood-pressure measuring apparatus

ABSTRACT

An apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, including a first blood-pressure measuring device which measures a first blood pressure of a right inferior limb of the subject, a second blood-pressure measuring device which measures a second blood pressure of a left inferior limb of the subject, a third blood-pressure measuring device which measures a third blood pressure of a superior limb of the subject, a first information obtaining device which obtains first information relating to a first velocity of propagation of a first pulse wave which propagates through a first route a portion of which runs in the right inferior limb, a second information obtaining device which obtains second information relating to a second velocity of propagation of a second pulse wave which propagates through a second route a portion of which runs in the left inferior limb, a selecting device for selecting one of the measured first and second blood pressures that corresponds to one of the first and second information that relates to a lower one of the first and second velocities, and an index determining device for determining the superior-and-inferior-limb blood-pressure index, based on the selected one of the first and second blood pressures, and the measured third blood pressure.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an apparatus for measuring asuperior-and-inferior-limb blood-pressure index of a living subject(e.g., a ratio of an inferior-limb blood pressure to a superior-limbblood pressure, or a ratio of a superior-limb blood pressure to aninferior-limb blood pressure), and to an apparatus for measuring a bloodpressure of an inferior limb of a living subject, the latter apparatusbeing advantageously employed by the former apparatus.

[0003] 2. Related Art Statement

[0004] For a person who suffers arterial obstruction or arteriostenosis,his or her inferior-limb blood pressure (“BP”) value is lower than hisor her corresponding superior-limb BP value (for example, a systolicsuperior-limb BP value corresponds to a systolic inferior-limb BPvalue). Meanwhile, if an inferior-limb BP value of a person is higherthan his or her corresponding superior-limb BP value by a prescribedvalue, he or she may suffer aortic incompetence or aortitis syndromelimited to aortic arch. It has been practiced to utilize this fordiagnosing arterial disease based on the ratio of inferior-limb BP valueto superior-limb BP value or the ratio of superior-limb BP value toinferior-limb BP value, that is, a superior-and-inferior-limb BP index.

[0005] Since the superior-and-inferior-limb BP index is simply obtainedas the ratio of inferior-limb BP value to superior-limb BP value or theratio of superior-limb BP value to inferior-limb BP value, it isrequired to measure accurately the inferior-limb BP value. However, ifone or more blood vessels running in a portion of an inferior limb fromwhich the inferior-limb BP value is measured suffer advancedcalcification, that is, sclerosis of tunica media as the middle one ofthree layers of tunica vasculosa, the inferior-limb BP value is raisedbecause of the hardness of the blood vessels. In addition, since aninferior limb is thicker than a superior limb and has a generallyconical shape, it is hard to wind an inflatable cuff around it.Moreover, since arterial vessels running in an inferior limb are presentdeep in adipose tissues and muscles, it is naturally harder to measurean inferior-limb BP value than measure a superior-limb BP value. In thecase where blood vessels running in a portion of an inferior limb fromwhich an inferior-limb BP value is measured suffer highly advancedcalcification, those blood vessels cannot be fully occluded by thepressing of an inflatable cuff and accordingly an excessively highinferior-limb BP value may be measured. Therefore, if a person whosuffers arterial obstruction or arteriostenosis also suffers advancedcalcification of his or her inferior-limb blood vessels, a normalsuperior-and-inferior-limb BP index value may be measured from theperson. In this case, arterial obstruction or arteriostenosis cannot beaccurately diagnoses based on the superior-and-inferior-limb BP index.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of the present invention to provide anapparatus which can measure a highly reliable superior-and-inferior-limbblood-pressure index of a living subject even if he or she may sufferthe calcification of his or her inferior-limb blood vessels.

[0007] It is another object of the present invention to provide anapparatus which measures a superior-and-inferior-limb blood-pressureindex of a living subject while judging whether the measurement of aninferior-limb blood pressure is abnormal.

[0008] It is another object of the present invention to provide anapparatus which measures an inferior-limb blood-pressure of a livingsubject while judging whether the subject suffers the calcification ofhis or her inferior-limb blood vessel.

[0009] (1) According to a first feature of the present invention, thereis provided an apparatus for measuring a superior-and-inferior-limbblood-pressure index of a living subject, comprising a firstblood-pressure measuring device which measures a first blood pressure ofa right inferior limb of the subject; a second blood-pressure measuringdevice which measures a second blood pressure of a left inferior limb ofthe subject; a third blood-pressure measuring device which measures athird blood pressure of a superior limb of the subject; a firstinformation obtaining device which obtains first information relating toa first velocity of propagation of a first pulse wave which propagatesthrough a first route a portion of which runs in the right inferiorlimb; a second information obtaining device which obtains secondinformation relating to a second velocity of propagation of a secondpulse wave which propagates through a second route a portion of whichruns in the left inferior limb; selecting means for selecting one of themeasured first and second blood pressures that corresponds to one of thefirst and second information that relates to a lower one of the firstand second velocities; and index determining means for determining thesuperior-and-inferior-limb blood-pressure index, based on the selectedone of the first and second blood pressures, and the measured thirdblood pressure.

[0010] According to this feature, the first information obtaining deviceobtains first information relating to a first velocity of propagation ofa first pulse wave which propagates through a first route a portion ofwhich runs in the right inferior limb, the second information obtainingdevice obtains second information relating to a second velocity ofpropagation of a second pulse wave which propagates through a secondroute a portion of which runs in the left inferior limb, the selectingmeans selects one of the measured first and second BP values thatcorresponds to one of the first and second information that relates to alower one of the first and second velocities, and the index determiningmeans determines the superior-and-inferior-limb BP index, based on theselected one of the first and second BP values, and the measured thirdBP value. The higher the degree of calcification of blood vessel is, thehigher the velocity of propagation of pulse wave through the bloodvessel is. Therefore, the selected one of the measured first and secondBP values that corresponds to the lower one of the first and secondvelocities, means the inferior-limb BP value measured from the lesscalcified inferior limb. Since this inferior-limb BP value, selected bythe selecting means, is used in determining thesuperior-and-inferior-limb BP index, a highly reliablysuperior-and-inferior-limb BP index value can be obtained.

[0011] (2) According to a second feature of the present invention thatincludes the first feature (1), the index determining means comprisesmeans for determining, as the superior-and-inferior-limb blood-pressureindex, a ratio of the selected one of the first and second bloodpressures to the third blood pressure, or a ratio of the third bloodpressure to the selected one of the first and second blood pressures.

[0012] (3) According to a third feature of the present invention thatincludes the first or second feature (1) or (2), the first informationobtaining device comprises two first pulse-wave sensors which are wornon two different first portions of the living subject, respectively, andeach of which detects the first pulse wave at a corresponding one of thetwo first portions, at least one of the two first portions belonging tothe right inferior limb, and the second information obtaining devicecomprises two second pulse-wave sensors which are worn on two differentsecond portions of the subject, respectively, and each of which detectsthe second pulse wave at a corresponding one of the two second portions,at least one of the two second portions belonging to the left inferiorlimb.

[0013] (4) According to a fourth feature of the present invention thatincludes the third feature (3), the first information obtaining devicecomprises first time determining means for determining, based onrespective times when the two first pulse-wave sensors detect the firstpulse wave, a first propagation time needed for the first pulse wave topropagate between the two different first portions of the livingsubject, and the second information obtaining device comprises secondtime determining means for determining, based on respective times whenthe two second pulse-wave sensors detect the second pulse wave, a secondpropagation time needed for the second pulse wave to propagate betweenthe two different second portions of the subject.

[0014] (5) According to a fifth feature of the present invention thatincludes the fourth feature (4), the first information obtaining devicecomprises first velocity determining means for determining, based on thedetermined first propagation time and a distance between the two firstportions of the living body, the first velocity of propagation of thefirst pulse wave, and wherein the second information obtaining devicecomprises second velocity determining means for determining, based onthe determined second propagation time and a distance between the twosecond portions of the living body, the second velocity of propagationof the second pulse wave.

[0015] (6) According to a sixth feature of the present invention, thereis provided an apparatus for measuring a superior-and-inferior-limbblood-pressure index of a living subject, comprising a firstblood-pressure measuring device which includes a first inflatable cuffadapted to be wound around an inferior limb of the subject and whichmeasures a first blood pressure of the inferior limb; a secondblood-pressure measuring device which measures a second blood pressureof a superior limb of the subject; a first pulse-wave sensor whichdetects a first pulse wave which propagates through a portion of theinferior limb that is located on an upstream side of the firstinflatable cuff; sharpness determining means for determining a degree ofsharpness of a heartbeat-synchronous pulse of the first pulse wavedetected by the first pulse-wave sensor; and judging means for judgingthat when the determined degree of sharpness is not greater than a firstreference value and the measured first blood pressure is higher than themeasured second blood pressure by a value not smaller than a secondreference value, the measurement of the first blood pressure by thefirst blood pressure measuring device is abnormal.

[0016] According to this feature, the sharpness determining meansdetermines a degree of sharpness of a heartbeat-synchronous pulse of thefirst pulse wave detected by the first pulse-wave sensor, and thejudging means judges that when the determined degree of sharpness is notgreater than a first reference value and the measured first bloodpressure is higher than the measured second blood pressure by a valuenot smaller than a second reference value, the measurement of the firstblood pressure by the first blood pressure measuring device is abnormal.Thus, an operator such as a medical staff can recognize that themeasurement of the first blood pressure has not been properly performedby the first blood pressure measuring device. A small degree ofsharpness, determined by the sharpness determining means, means that thesubject suffers arteriostenosis in the portion of the inferior limblocated on the upstream side of the first inflatable cuff andaccordingly a lowered BP value is measured from a portion of theinferior limb located on a downstream side of the cuff. If it is assumedthat the BP measurement has been properly performed, the determineddegree of sharpness which is not greater than the first reference valueshould mean that the measured inferior-limb BP value is equal to, orlower than the superior-limb BP value. When, in fact, the measuredinferior-limb BP value is higher than the superior-limb BP value by avalue not smaller than the second reference value, it can therefore beconcluded that the BP measurement was abnormal because the blood blowthrough the blood vessel or vessels running in the portion of theinferior limb pressed by the cuff cannot be fully stopped by the cuff.

[0017] (7) According to a seventh feature of the present invention thatincludes the sixth feature (6), the second blood-pressure measuringdevice comprises a second inflatable cuff adapted to be wound around thesuperior limb of the subject, and wherein the apparatus furthercomprises a second pulse-wave sensor which detects a second pulse wavewhich propagates through a portion of the superior limb that is locatedon an upstream side of the second inflatable cuff; and reference-valuedetermining means for determining the first reference value based on thesecond pulse wave detected by the second pulse-wave sensor.

[0018] (8) According to an eighth feature of the present invention thatincludes the sixth or seventh feature (6) or (7), the sharpnessdetermining means comprises means for determining, as the degree ofsharpness, a percentage, %MAP, of a height of a center of gravity of anarea enveloped by a waveform of the heartbeat-synchronous pulse of thefirst pulse wave, relative to an amplitude of the waveform of the pulse.

[0019] (9) According to a ninth feature of the present invention, thereis provided an apparatus for measuring a superior-and-inferior-limbblood-pressure index of a living subject, comprising a firstblood-pressure measuring device which includes an inflatable cuffadapted to be wound around an inferior limb of the subject and whichmeasures a first blood pressure of the inferior limb; a secondblood-pressure measuring device which measures a second blood pressureof a superior limb of the subject; a first pulse-wave sensor whichdetects a first pulse wave which propagates through a portion of theinferior limb that is located on an upstream side of the inflatablecuff; a second pulse-wave sensor which detects a second pulse wave whichpropagates through the superior limb; and a display device whichsimultaneously displays the measured first and second blood pressuresand the detected first and second pulse waves.

[0020] According to this feature, the display device simultaneouslydisplays the measured first and second blood pressures and the detectedfirst and second pulse waves. Therefore, if the first or inferior-limbBP value is higher than the second or superior-limb BP value but anobserver can see on the display device that the first or inferior-limbpulse wave is less sharp than the second or superior-limb pulse wave,the observer can judge that the BP measurement peformed by the first orinferior-limb BP measuring device was abnormal.

[0021] (10) According to a tenth feature of the present invention thatincludes the ninth feature (9), the apparatus further comprises indexdetermining means for determining a superior-and-inferior-limbblood-pressure index of the subject, based on the measured first andsecond blood pressures, and the display device displays the determinedsuperior-and-inferior-limb blood-pressure index, in addition to themeasured first and second blood pressures and the detected first andsecond pulse waves.

[0022] (11) According to an eleventh feature of the present invention,there is provided an apparatus for measuring a blood pressure of aninferior limb of a living subject, comprising a blood-pressure measuringdevice which includes an inflatable cuff adapted to be wound around theinferior limb and which measures,-with the cuff, the blood pressure ofthe inferior limb of the subject; an input device which is operable forinputting at least one characteristic value characteristic of thesubject and which produces at least one signal representing the at leastone input characteristic value; map selecting means for selecting, basedon the input characteristic value, one of a plurality of predeterminedmaps each of which defines, in a coordinate system having a first axisrepresenting blood pressure and a second axis representing informationrelating to velocity of propagation of pulse wave through blood vessel,a calcification range indicating calcification of the blood vessel; aninformation obtaining device which obtains information relating to avelocity of propagation of a pulse wave which propagates between twodifferent portions of the subject that include a portion of the inferiorlimb around which the inflatable cuff is wound; and judging means forjudging whether the measured blood pressure and the obtained informationfall in the calcification range of the selected map, and thereby judgingwhether at least one blood vessel running in the portion of the inferiorlimb has been calcified to such a degree that a blood flow through theblood vessel cannot be stopped by the inflatable cuff.

[0023] According to this feature, the map selecting means selects, basedon the input characteristic value, one of a plurality of predeterminedmaps each of which defines, in a coordinate system having a first axisrepresenting blood pressure and a second axis representing informationrelating to velocity of propagation of pulse wave through blood vessel,a calcification range indicating calcification of the blood vessel, andthe judging means judges whether the measured blood pressure and theobtained information fall in the calcification range of the selectedmap, and thereby judges whether at least one blood vessel running in theportion of the inferior limb has been calcified to such a degree that ablood flow through the blood vessel cannot be stopped by the inflatablecuff. Therefore, an operator can recognize that the BP measurementperformed by the BP measuring device was abnormal.

[0024] (12) According to a twelfth feature of the present invention thatincludes the eleventh feature (11), the input device comprises means forinputting, as the at least one characteristic value, at least one valueselected from the group consisting of an age of the subject, a valuecorresponding to a sex of the subject, and a height of the subject.

[0025] (13) According to a thirteenth feature of the present inventionthat includes the eleventh or twelfth feature (11) or (12), theapparatus further comprises a memory which stores the plurality ofpredetermined maps.

[0026] (14) According to a fourteenth feature of the present inventionthat includes any one of the eleventh to thirteenth features (11) to(13), the information obtaining device comprises propagation-timemeasuring means for measuring a time needed for the pulse wave topropagate between the two different portions of the subject.

[0027] (15) According to a fifteenth feature of the present inventionthat includes the fourteenth feature (14), the information obtainingdevice further comprises inverse-of-propagation-time determining meansfor determining, as the information, an inverse of the propagation timemeasured by the propagation-time measuring means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and optional objects, features, and advantages of thepresent invention will be better understood by reading the followingdetailed description of the preferred embodiments of the invention whenconsidered in conjunction with the accompanying drawings, in which:

[0029]FIG. 1 is a diagrammatic view of the construction of an ankle/armblood-pressure (“BP”) index measuring apparatus to which the presentinvention is applied;

[0030]FIG. 2 is a diagrammatic view of important control functions of anelectronic control device of the measuring apparatus of FIG. 1;

[0031]FIG. 3 is a view showing an example of a right pulse-wavepropagation time, DT_(R), determined by the operation of the controldevice of the measuring device of FIG. 1;

[0032]FIG. 4 is a flow chart representing a control program according towhich the control device of the measuring apparatus of FIG. 1 isoperated;

[0033]FIG. 5 is a diagrammatic view of important control functions of anelectronic control device of an ankle/arm BP index measuring apparatusas a second embodiment of the present invention;

[0034]FIG. 6 is a flow chart representing a control program according towhich the control device of the measuring apparatus of FIG. 5 isoperated;

[0035]FIG. 7 is a view showing an example of a screen image displayed bya display device of the measuring apparatus of FIG. 5;

[0036]FIG. 8 is a diagrammatic view of the construction of an ankle/armBP index measuring apparatus as the third embodiment of the presentinvention;

[0037]FIG. 9 is a diagrammatic view of important control functions of anelectronic control device of the measuring apparatus of FIG. 8; and

[0038]FIG. 10 is a view showing an example of a map selected by a mapselecting means of the measuring device of FIG. 8; and

[0039]FIG. 11 is a flow chart representing a control program accordingto which the control device of the measuring apparatus of FIG. 8 isoperated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, there will be described an ankle/arm blood-pressure(“BP”) index measuring apparatus 10 to which the present invention isapplied, by reference to the drawings. FIG. 1 is a block diagram showingthe construction of the measuring apparatus 10. The ankle/arm BP indexmeasuring apparatus 10 is a sort of superior-and-inferior-limb BP indexmeasuring apparatus, since the measuring apparatus 10 measures, as aninferior-limb BP value, a BP value from an ankle of a patient as aliving person and measures, as a superior-limb BP value, a BP value froman upper arm of the patient. The present apparatus 10 carries out the BPmeasurements on the patient who takes the facedown, lateral, or face-upposition so that the upper arm and the ankle are substantially levelwith each other.

[0041] In FIG. 1, the ankle/arm BP index measuring apparatus 10 includesa right-ankle BP measuring device 14 which measures a BP value from aright ankle 12 of the patient, a left-ankle BP measuring device 18 whichmeasures a BP value from a left ankle 16 of the patient, and anupper-arm BP measuring device 22 which measures a BP value from an upperarm 20 of the patient.

[0042] The right-ankle BP measuring device 14 includes an inflatablecuff 24 which includes a belt-like cloth bag and a rubber bagaccommodated in the cloth bag and which is wound around the right ankle12 of the patient; a piping 26; and a pressure sensor 28, a switch valve30, and an air pump 32 which are connected to the cuff 24 via the piping26. The switch valve 30 is selectively placed in one of three operationstates, that is, (a) a pressurized-air-supply state in which the switchvalve 30 allows pressurized air to be supplied from the air pump 32 tothe cuff 24, (b) a slow-deflation state in which the valve 30 allows thepressurized air to be deflated slowly from the cuff 24, and (c) aquick-deflation state in which the valve 30 allows the pressurized airto be deflated quickly from the cuff 24.

[0043] The pressure sensor 28 detects an air pressure in the cuff 24,and supplies a pressure signal, SP₁, representing the detected airpressure, to a static-pressure filter circuit 34 and a pulse-wave filtercircuit 36. The static-pressure filter circuit 34 includes a low-passfilter which allows only low frequencies to pass therethrough andthereby selects, from the pressure signal SP₁, a cuff-pressure signal,SK₁, representing a cuff pressure, P_(C1), as the constant component ofthe detected air pressure. The filter circuit 34 supplies thecuff-pressure signal SK₁ to an electronic control device 38 via ananalog-to-digital (“A/D”) converter (not shown).

[0044] The pulse-wave filter circuit 36 includes a band-pass filterwhich allows only specific frequencies to pass therethrough and therebyselects, from the pressure signal SP₁, a pulse-wave signal, SM₁,representing a pulse wave as the oscillatory component of the detectedair pressure. The filter circuit 36 supplies the pulse-wave signal SM₁to the electronic control device 38 via an A/D converter (not shown).

[0045] The left-ankle BP measuring device 18 includes an inflatable cuff40, a piping 42, a pressure sensor 44, and a switch valve 46 which haverespective constructions identical with those of the counterparts 24,26, 28, 30 of the right-ankle BP measuring device 14. The cuff 40 of theleft-ankle BP measuring device 18 is wound around a portion of the leftankle 16 that corresponds to a portion of the right ankle 12 aroundwhich the cuff 24 of the right-ankle BP measuring device 14 is wound.The switch valve 46 is connected to the air pump 32. The pressure sensor44 detects an air pressure in the cuff 40, and supplies a pressuresignal, SP₂, representing the detected air pressure, to astatic-pressure filter circuit 48 and a pulse-wave filter circuit 50which have respective constructions identical with those of thecounterparts 34, 36 of the right-ankle BP measuring device 14. Thestatic-pressure filter circuit 48 selects, from the pressure signal SP₂,a cuff-pressure signal, SK₂, representing a cuff pressure, P_(C2), asthe constant component of the detected air pressure, and supplies thecuff-pressure signal SK₂ to the control device 38 via an A/D converter(not shown). The pulse-wave filter circuit 50 selects, from the pressuresignal SP₂, a pulse-wave signal, SM₂, representing a pulse wave as theoscillatory component of the detected air pressure, and supplies thepulse-wave signal SM₂ to the control device 38 via an A/D converter (notshown).

[0046] The upper-arm BP measuring device 22 includes an inflatable cuff52 which has a construction identical with the cuff 24 or 40 and whichis wound around an upper arm 20 (e.g., a right upper arm) of thepatient; and a piping 54, a pressure sensor 56, and a switch valve 58which have respective constructions identical with those of thecounterparts 24, 26, 28, 30 of the right-ankle BP measuring device 14.The switch valve 58 is connected to the air pump 32. The pressure sensor56 detects an air pressure in the cuff 52, and supplies a pressuresignal, SP₃, representing the detected air pressure, to astatic-pressure filter circuit 60 and a pulse-wave filter circuit 62which have respective constructions identical with those of thecounterparts 34, 36 of the right-ankle BP measuring device 14. Thestatic-pressure filter circuit 60 selects, from the pressure signal SP₃,a cuff-pressure signal, SK₃, representing a cuff pressure, P_(C3), asthe constant component of the detected air pressure, and supplies thecuff-pressure signal SK₃ to the control device 38 via an A/D converter(not shown). The pulse-wave filter circuit 62 selects, from the pressuresignal SP₃, a pulse-wave signal, SM₃, representing a pulse wave as theoscillatory component of the detected air pressure, and supplies thepulse-wave signal SM₃ to the control device 38 via an A/D converter (notshown).

[0047] The electronic control device 38 is essentially provided by amicrocomputer including a central processing unit (“CPU”) 64, a readonly memory (“ROM”) 66, a random access memory (“RAM”) 68, and aninput-and-output (“I/O”) port (not shown), and processes input signalsaccording to control programs pre-stored in the ROM 66, while utilizingthe temporary-storage function of the RAM 68. The control device 38outputs, from the I/O port, drive signals to the air pump 32 and thethree switch valves 30, 46, 58 so as to control the respectiveoperations thereof, and display signals to a display device 70 so as tocontrol the contents displayed thereby.

[0048] An electrocardiograph (“ECG”) 72 includes a plurality ofelectrodes 74 adapted to be attached to predetermined portions of thepatient, and continuously detects an electrocardiogram representing theactive potential of the heart muscle of the patient. The ECG 72 suppliesan ECG signal, SM₄, representing the detected electrocardiogram, to theelectronic control device 38. The electrocariogram detected by the ECG72 includes, as shown in FIG. 3, a Q wave or an R wave that correspondsto a time when the heart starts outputting blood toward the aorta. Thus,the ECG 72 functions as a first pulse-wave sensor.

[0049]FIG. 2 is a diagrammatic view for explaining the important controlfunctions of the control device 38. A cuff-pressure regulating means 80controls, in each BP measuring operation, the air pump 32 and the threeswitch valves 30, 46, 58 each connected thereto, such that therespective pressing pressures of the three cuffs 24, 40, 52 are quicklyincreased up-to a predetermined target pressure value, SCM, (e.g., about180 mmHg) and then are slowly decreased at a rate of about 3 mmHg/sec.In each pulse-wave detecting operation carried out for obtaininginformation relating to velocity of propagation of pulse wave, thecuff-pressure regulating means 80 controls the air pump 32 and the twoswitch valves 30, 46 each connected thereto, such that the respectivepressing pressures P_(C1), P_(C2) of the two cuffs 24, 40 are quicklyincreased up to a predetermined target pressure value which issufficiently lower than a diastolic BP value of the patient, and thenare maintained at the target pressure for a predetermined time duration.

[0050] A right-ankle BP determining means 82 determines right-anklesystolic and diastolic BP values, BP_(RSYS), BP_(RDIA), etc., that is,BP values of the right ankle 12, according to well-known oscillometricmethod, based on the change of respective amplitudes of theheartbeat-synchronous pulses of the pulse-wave signal SM₁ detected oneby one during the slow deflation of the cuff 24 wound around the rightankle 12 under the control of the cuff-pressure regulating means 80.

[0051] A left-ankle BP determining means 84 determines left-anklesystolic and diastolic BP values, BP_(LSYS), BP_(LDIA), etc., that is,BP values of the left ankle 16, according to the oscillometric method,based on the change of respective amplitudes of theheartbeat-synchronous pulses of the pulse-wave signal SM₂ detected oneby one during the slow deflation of the cuff 40 wound around the leftankle 16 under the control of the cuff-pressure regulating means 80.

[0052] An upper-arm BP determining means 86 determines upper-armsystolic and diastolic BP values, BP_(ASYS), BP_(ADIA), etc., that is,BP values of the upper arm 20, according to the oscillometric method,based on the change of respective amplitudes of theheartbeat-synchronous pulses of the pulse-wave signal SM₃ detected oneby one during the slow deflation of the cuff 52 wound around the upperarm 20 under the control of the cuff-pressure regulating means 80.

[0053] A right pulse-wave-propagation-velocity (“PWV”) relatinginformation obtaining means 88 obtains information relating to avelocity of propagation of a pulse wave which propagates through a rightpulse-wave propagation route including a portion thereof running in theright inferior limb. More specifically, the rightPWV-relating-information obtaining means 88 obtains information relatingto a velocity of propagation of a pulse wave between two portions of thepatient, based on a second pulse wave detected by a right secondpulse-wave sensor worn on a portion of the right inferior limb that islocated on an upstream side of the cuff 24 wound around the right ankle12, i.e., on a proximal side of the cuff 24 (this upstream-side portionof the right inferior limb may be a portion thereof around which thecuff 24 is wound), and a first pulse wave detected by a right firstpulse-wave sensor worn on a proximal side of the right second pulse-wavesensor. For example, the right PWV-relating-information obtaining means88 determines, as the right PWV-relating information, a right PWV value,V_(R), or a right pulse-wave propagation time, DT_(R), based on a timedifference between a periodic point on each of heartbeat-synchronouspulses of the first pulse wave, and a periodic point on a correspondingone of heartbeat-synchronous pulses of the second pulse wave. The ECG 72functions as the right first pulse-wave sensor, and the pulse-wavefilter circuit 36 of the right-ankle BP measuring device 14 that detectsa pulse wave from the posterior tibial artery running in the portion ofthe right ankle 12 around which the cuff 24 is wound, functions as thesecond pulse-wave sensor. The right PWV-relating-information obtainingmeans 88 includes a time-difference calculating means which calculates atime difference (i.e., right pulse-wave propagation time), DT_(R), shownin FIG. 3, that is, a time difference between a time point at which theECG 72 detects the R wave of each heartbeat-synchronous pulse of theelectrocardiogram (i.e., ECG waveform), and a time point at which thefilter circuit 36 detects the rising point (i.e., the lowest point) of acorresponding heartbeat-synchronous pulse of the posterior-tibial-arterypulse wave. The right PWV-relating-information obtaining means 88iteratively calculates, based on the calculated time difference DT_(R)calculated by the time-difference calculating means for each of theheartbeat-synchronous pulses, a right PWV value V_(R) (m/sec), accordingto the following expression (1) pre-stored in the ROM 66:

V _(R) =L _(R)/(DT _(R) −T _(PEP))  (1)

[0054] where L_(R) (m) is the distance from the left ventricle of theheart, via the aorta, to the portion of the right ankle 12 around whichthe cuff 24 is wound; and T_(PEP) (sec) is a pre-ejection time betweenthe R wave of the ECG waveform and the rising point of the aortic pulsewave, as shown in FIG. 3 (L_(R) and T_(PEP) are replaced with respectiveconstant values which are experimentally obtained in advance).

[0055] Like the right PWV-relating-information obtaining means 88, aleft PWV-relating-information obtaining means 90 obtains informationrelating to a velocity of propagation of a pulse wave which propagatesthrough a left pulse-wave propagation route including a portion thereofrunning in the left inferior limb. More specifically, the leftPWV-relating-information obtaining means 90 obtains information relatingto a velocity of propagation of a pulse wave between two portions of thepatient, based on a second pulse wave detected by a left secondpulse-wave sensor worn on a portion of the left inferior limb that islocated on an upstream side of the cuff 40 wound around the left ankle16, i.e., on a proximal side of the cuff 40 (the upstream-side portionof the left inferior limb may be a portion thereof around which the cuff40 is wound), and a first pulse wave detected by a left first pulse-wavesensor worn on a proximal side of the left second pulse-wave sensor. Theleft first and second pulse-wave sensors are worn on the patient,symmetrically with the right first and second pulse-wave sensors, withrespect to the centerline of the patient. Thus, the distance between thecuff 40 and each of the left first and second pulse-wave sensors isequal to the distance between the cuff 24 and a corresponding one of theright first and second pulse-wave sensors. The ECG 72 functioning as theright first pulse-wave sensor also functions as the left firstpulse-wave sensor, and the pulse-wave filter circuit 50 of theleft-ankle BP measuring device 18 functions as the left secondpulse-wave sensor. The left PWV-relating-information obtaining means 90includes a time-difference calculating means which calculates a timedifference (i.e., left pulse-wave propagation time), DT_(L), that is, atime difference between a time point at which the ECG 72 detects the Rwave of each heartbeat-synchronous pulse of the ECG waveform, and a timepoint at which the filter circuit 50 detects the rising point (i.e., thelowest point) of a corresponding heartbeat-synchronous pulse of theposterior-tibial-artery pulse wave. The left PWV-relating-informationobtaining means 90 iteratively calculates, based on the calculated timedifference DT_(L) calculated by the time-difference calculating meansfor each of the heartbeat-synchronous pulses, a left PWV value V_(R)(m/sec), according to the following expression (2) pre-stored in the ROM66:

V _(L) =L _(L)/(DT _(L) −T _(PEP))  (2)

[0056] where L_(L) (m) is the distance from the left ventricle of theheart, via the aorta, to the portion of the left ankle 16 around whichthe cuff 40 is wound. (L_(L) is replaced with a constant value which isexperimentally obtained in advance).

[0057] A BP selecting means 92 compares the right PWV-relatinginformation obtained by the means 88 and the left PWV-relatinginformation obtained by the means 90, with each other, and selects oneof the right-ankle BP value BP_(R) determined by the right-ankle BPdetermining means 82 and the corresponding left-ankle BP value BP_(L),determined by the left-ankle BP determining means 84, so that theselected ankle BP value is used by an ankle/arm BP index determiningmeans 94, described below, to determine an ankle/arm BP index (“API”).More specifically described, the selecting means 92 selects, as theankle BP value, one of the right-ankle and left-ankle BP values BP_(R),BP_(L), that corresponds to the lower one of the right and leftpropagation velocities V_(R), V_(L), or the longer one of the right andleft propagation times DT_(R), DT_(L).

[0058] An API determining means 94 determines or calculates an API valuebased on the inferior-limb BP value selected by the BP selecting means92 and the corresponding upper-arm BP value BP_(A) determined by theupper-arm BP determining means 86. For example, in the case where the BPselecting means 92 selects the right-ankle systolic BP value BP_(RSYS),the API may be obtained by dividing the right-ankle systolic BP valueBP_(RSYS) by the upper-arm systolic BP value BP_(ASYS), or dividing theupper-arm systolic BP value BP_(ASYS) by the right-ankle systolic BPvalue BP_(RSYS). The thus determined API value is displayed on thedisplay device 70.

[0059]FIG. 4 is a flow chart representing a control program according towhich the control device 38 is operated. First, the control of thecontrol device 38 starts with Steps S1, S2, and S3 corresponding to thecuff-pressure regulating means 80. At Step SA1, the three switch valves30, 46, 58 are switched to their pressure-supply positions and the airpump 32 is operated, so that the respective air pressures of the threecuffs 24, 40, 52 are quickly increased. At Step SA2, it is judgedwhether all the air pressures PC of the three cuffs 24, 40, 52 havereached the predetermined target pressure value PCM (about 180 mmHg). Ifa negative judgment is made at Step SA2, Steps SA1 and SA2 are repeatedto continue increasing the air pressures P_(C) of the cuffs 24, 40, 52.

[0060] If a positive judgment is made at Step SA2, the control goes toStep SA3 to stop the operation of the air pump 32 and switch the threeswitch valves 30, 46, 58 to their slow-deflation positions, so that therespective air pressures P_(C) of the three cuffs 24, 40, 52 aredecreased slowly at a predetermined low rate of about 3 mmHg/sec.

[0061] Step SA3 is followed by the BP-determine routine of Step SA4,corresponding to the right-ankle BP determining means 82, the left-ankleBP determining means 84, and the upper-arm BP determining means 86. Morespecifically described, the control device 38 determines an amplitude ofeach of successive heartbeat-synchronous pulses of the cuff pulse waverepresented by the pulse-wave signal SM₁ supplied from the pulse-wavefilter circuit 36, and determines a right-ankle systolic BP valueBP_(RSYS), etc. based on the timewise change of the thus determinedamplitudes according to a well-known oscillometric BP-determinealgorithm. Similarly, the control device 38 determines an amplitude ofeach of successive heartbeat-synchronous pulses of the cuff pulse waverepresented by the pulse-wave signal SM₂ supplied from the pulse-wavefilter circuit 50, and determines a left-ankle systolic BP valueBP_(LSYS), etc. based on the timewise change of the thus determinedamplitudes according to the oscillometric BP-determine algorithm. Inaddition, the control device 38 determines an amplitude of each ofsuccessive heartbeat-synchronous pulses of the cuff pulse waverepresented by the pulse-wave signal SM₃ supplied from the pulse-wavefilter circuit 62, and determines an upper-arm systolic BP valueBP_(ASYS), etc. based on the timewise change of the thus determinedamplitudes according to the oscillometric BP-determine algorithm.

[0062] Step SA4 is followed by Step SA5 corresponding to thecuff-pressure regulating means 80. At Step SA5, the three switch valves30, 46, 58 are switched to their quick-deflation positions, so that therespective air pressures of the three cuffs 24, 40, 52 are quicklydecreased.

[0063] Step SA5 is followed by Step SA6 corresponding to thecuff-pressure regulating means 80. At Step SA6, the two switch valve 30,46 connected to the two cuffs 24, 40 respectively wound around the rightand left ankles 12, 16, are switched, for determining the right and leftpulse-wave propagation times DT_(R), DT_(L), to their pressure-supplypositions, so that the respective air pressures P_(C1), P_(C2) of thetwo cuffs 24, 40 are increased up to a predetermined target value whichis estimated to be sufficiently lower than the diastolic BP value of thepatient, and then are maintained at the target value.

[0064] Step SA6 is followed by Step SA7 to judge, based on the ECGsignal SM₄ supplied from the ECG 72, whether the ECG 72 has detected theR wave of a heartbeat-synchronous pulse of the ECG waveform. If anegative judgment is made at Step SA7, Step SA7 is repeated. Meanwhile,if a positive judgment is made, the control of the control device 38goes to Step SA8 to judge, based on the pulse-wave signal SM₁ suppliedfrom the pulse-wave filter circuit 36 of the right-ankle BP measuringdevice 14, whether the filter circuit 36 has detected the rising pointof a heartbeat-synchronous pulse of the right-posterior-tibial-arterywaveform.

[0065] If a negative judgment is made at Step SA8, the control skipsStep SA9 and carries out Step SA10. Meanwhile, if a positive judgment ismade at Step SA8, the control of the control device 38 goes to Step SA9corresponding to the right PWV-relating-information obtaining means 88.At Step SA9, the control device 38 calculates, as shown in FIG. 3, atime difference between a time when the R wave is detected by the ECG 72and a time when the rising point of the right-posterior-tibial-arterywaveform is detected, i.e., a right pulse-wave propagation time DT_(R)that is a time needed for a pulse wave to propagate from the heart tothe portion of the right inferior limb (i.e., the right leg) aroundwhich the cuff 24 is wound.

[0066] At the following Step SA10, the control device 38 judges, basedon the pulse-wave signal SM₂ supplied from the pulse-wave filter circuit50 of the left-ankle BP measuring device 18, whether the filter circuit50 has detected the rising point of a heartbeat-synchronous pulse of theleft-posterior-tibial-artery waveform. If a negative judgment is made atStep SA10, the control skips Step SA11 and carries out Step SA12.Meanwhile, if a positive judgment is made at Step SA10, the control ofthe control device 38 goes to Step SA11 corresponding to the leftPWV-relating-information obtaining means 90. At Step SA11, the controldevice 38 calculates a time difference between a time when the R wave isdetected by the ECG 72 and a time when the rising point of theleft-posterior-tibial-artery waveform is detected, i.e., a leftpulse-wave propagation time DT_(L) that is a time needed for a pulsewave to propagate from the heart to the portion of the left inferiorlimb (i.e., the left leg) around which the cuff 40 is wound.

[0067] At the following Step SA12, the control device 38 judges whetherthe control device 38 has determined both the right and left pulse-wavepropagation times DT_(R), DT_(L). If a negative judgment is made at StepSA12, Steps SA8 to SA12 are repeated. Meanwhile, if a positive judgmentis made at Step SA12, the control of the control device 38 goes to StepSA13 corresponding to the cuff-pressure regulating means 80. At StepSA13, the two switch valves 30, 46 are switched to their quick-deflationpositions, so that the respective air pressures of the two cuffs 24, 40are quickly decreased.

[0068] Step SA13 is followed by Step SA14 corresponding to the BPselecting means 92. At Step SA14, the control device 38 compares theright and left pulse-wave propagation times DT_(R), DT_(L) determined atStep SA9, with each other, and selects one of the right-ankle andleft-ankle systolic BP values BP_(RSYS), BP_(LSYS) that corresponds tothe longer one of the right and left pulse-wave propagation timesDT_(R), DT_(L). The thus selected ankle systolic BP value is used indetermining an API value at the next step.

[0069] Step SA14 is followed by Step SA15 corresponding to the ankle/armBP index determining means 94. At Step SA15, the control device 38calculates an API value by dividing the ankle systolic BP value selectedat Step SA14, by the upper-arm systolic BP value BP_(ASYS) determined atStep SA4. The thus determined API value is displayed on the displaydevice 70.

[0070] As is apparent from the foregoing description, the rightPWV-relating-information obtaining means 88 (Step SA9) obtains the rightpulse-wave propagation time DT_(R) needed for the pulse wave topropagate from the heart to the right ankle 12 around which the cuff 24is wound; the left PWV-relating-information obtaining means 90 (StepSA11) obtains the left pulse-wave propagation time DT_(L) needed for thepulse wave to propagate from the heart to the left ankle 16 around whichthe cuff 40 is wound; the BP selecting means 92 (Step SA14) selects oneof the right-ankle and left-ankle systolic BP values that corresponds tothe longer one of the right and left pulse-wave propagation timesDT_(R), DT_(L). The thus selected ankle systolic BP value corresponds toone of the two inferior limbs (i.e., the two legs) that has been lesscalcified than the other. Since the selected ankle systolic BP value isused in determining the API value, the thus determined API value enjoyshigh reliability.

[0071] Next, there will be described a second embodiment of the presentinvention that relates to an ankle/arm BP index measuring apparatus 100.The present apparatus 100 differs from the apparatus 10, shown in FIG.1, only in that the present apparatus 100 does not employ the ECG 72 andthe electrodes 74 employed in the apparatus 10 and that an electroniccontrol device 38 of the present apparatus 100 has different controlfunctions. Accordingly, the same reference numerals as used in the firstembodiment shown in FIGS. 1 to 4 are used to designate the correspondingelements and parts of the second embodiment shown in FIGS. 5 to 7, andthe description thereof is omitted.

[0072]FIG. 5 is a diagrammatic view for explaining important controlfunctions of the control device 38.

[0073] An inferior-limb pulse-wave-sharpness determining means 102determines a degree of sharpness of a heartbeat-synchronous pulse of afirst inferior-limb pulse wave detected by a first inferior-limbpulse-wave sensor worn on an upstream-side portion of the right inferiorlimb that is located on an upstream side of the cuff 24 wound around theright ankle 12 (the upstream-side portion of the right inferior limb maybe a portion thereof around which the cuff 24 is wound), andadditionally determines a degree of sharpness of a heartbeat-synchronouspulse of a second inferior-limb pulse wave detected by a secondinferior-limb pulse-wave sensor worn on an upstream-side portion of theleft inferior limb that is located on an upstream side of the cuff 40wound around the left ankle 16 (the upstream-side portion of the leftinferior limb may be a portion thereof around which the cuff 40 iswound). The pulse-wave filter circuit 36 connected to the cuff 24 viathe pressure sensor 28 functions as the first inferior-limb pulse-wavesensor, and the second pulse-wave filter circuit 50 connected to thecuff 40 via the pressure sensor 44 functions as the second inferior-limbpulse-wave sensor. The inferior-limb pulse-wave-sharpness determiningmeans 102 determines a degree of sharpness of a heartbeat-synchronouspulse of the pulse wave detected from the right posterior tibial arteryby the filter circuit 36, and determines a degree of sharpness of aheartbeat-synchronous pulse of the pulse wave detected from the leftposterior tibial artery by the filter circuit 50. The degree ofsharpness means a degree of sharpness of upward projection of aheartbeat-synchronous pulse. For example, the degree of sharpness may bean index, %MAP, which is defined as a percentage of a height, a, of acenter of gravity of an area enveloped by a heartbeat-synchronous pulse,relative to an amplitude, b, of the pulse. The height a indicates a meanBP value, MAP, and the amplitude b indicates a pulse pressure obtainedby subtracting a diastolic BP value from a systolic BP value. That is,the index %MAP is obtained according to the following expression (3):

%MAP=100×a/b  (3)

[0074] A superior-limb pulse-wave-sharpness determining means 104determines a degree of sharpness of a heartbeat-synchronous pulse of asuperior-limb pulse wave detected by a superior-limb pulse-wave sensorworn on an upstream-side portion of the superior limb that is located onan upstream side of the cuff 52 wound around the upper arm 20 (theupstream-side portion of the superior limb may be a portion thereofaround which the cuff 52 is wound). The pulse-wave filter circuit 62connected to the cuff 52 via the pressure sensor 56 functions as thesuperior-limb pulse-wave sensor, and the superior-limbpulse-wave-sharpness determining means 104 determines, like the means102, a degree of sharpness of a heartbeat-synchronous pulse of theupper-arm pulse wave detected by the filter circuit 62.

[0075] A BP-measurement-abnormality judging means 106 judges that whenthe degree of sharpness of the right-posterior-tibial-artery pulse wavedetermined by the means 102 is not greater than a reference value, TH,and the measured right-ankle BP value BP_(L) is higher than the measuredcorresponding upper-arm BP value BP_(A) by a value not smaller than areference value, α, the BP determination of the right-ankle BPdetermining means 82 is abnormal, and judges that when the degree ofsharpness of the left-posterior-tibial-artery pulse wave determined bythe means 102 is not greater than the reference value TH, and themeasured left-ankle BP value BP_(L) is higher than the measuredcorresponding upper-arm BP value BP_(A) by a value not smaller than thereference value α, the BP determination of the left-ankle BP determiningmeans 84 is abnormal. The reference value TH may be a constant valuewhich is determined based on a normal degree of sharpness of a pulse ofposterior-tibial-artery pulse wave. However, since, for a person whodoes not suffer inferior-limb arterial stenosis, a degree of sharpnessof posterior-tibial-artery pulse wave is greater than that ofbrachial-artery pulse wave, the degree of sharpness of the upper-armpulse wave determined by the means 104 may be used as the referencevalue TH. In the latter case, the superior-limb pulse-wave-sharpnessdetermining means 104 functions as a reference-value determining means.The reference value α is experimentally determined in advance, and avalue about 10 mmHg may be employed as the value α.

[0076] A BP-measurement-abnormality displaying means 108 controls, ifthe BP-measurement-abnormality judging means 106 judges that the BPdetermination of the right-ankle BP determining means 82 is abnormal,and/or that the BP determination of the left-ankle BP determining means84 is abnormal, the display device 70 to display characters or symbolsindicating that the BP determination of the right-ankle BP determiningmeans 82 is abnormal and/or that the BP determination of the left-ankleBP determining means 84 is abnormal.

[0077] An ankle/arm BP index determining means 110 determines a rightankle/arm BP index value (=API_(R)) based on the right-ankle BP valueBP_(R) determined by the means 82 and the upper-arm BP value BP_(A)(corresponding to the right-ankle BP value BP_(R)) determined by themeans 86, and determines a left ankle/arm BP index-value (=API_(L))based on the left-ankle BP value BP_(L) determined by the means 84 andthe upper-arm BP value BP_(A).

[0078] A pulse-wave displaying means 112 controls the display device 70to display, together with the right-ankle BP value BP_(R), theleft-ankle BP value BP_(L), and the upper-arm BP value BP_(A),respective waveforms of the right-posterior-tibial-artery pulse wave,the left-posterior-tibial-artery pulse wave, and the brachial-arterypulse-wave which are respectively detected by the pulse-wave filtercircuits 36, 50, 62 in a state in which the respective air pressuresP_(C1), P_(C2), P_(C3) of the three cuffs 24, 40, 52 are held at apressure value sufficiently lower than the diastolic BP value of thepatient.

[0079]FIG. 6 is a flow chart representing a control program according towhich the control device 38 of the ankle/arm BP index measuringapparatus 100 is operated. In FIG. 6, Steps SB1 to SB5 are identicalwith Steps SA1 to SA5 of the flow chart, shown in FIG. 4, which isemployed in the first embodiment. Thus, the apparatus 100 determines aright-ankle systolic BP value BP_(RSYS), a left-ankle systolic BP valueBP_(LSYS), and an upper-arm systolic BP value BP_(ASYS), and deflatesthe respective air pressures P_(C1), P_(C2), P_(C3) of the three cuffs24, 40, 52.

[0080] Step SB5 is followed by Step SB6 corresponding to the ankle/armBP index determining means 110. At Step SB6, the control device 38determines an index value API_(R) by dividing the right-ankle systolicBP value BP_(RSYS) determined at Step SB4 by the upper-arm systolic BPvalue BP_(ASYS) determined at the same step, and determines an indexvalue API_(L) by dividing the left-ankle systolic BP value BP_(LSYS)determined at Step SB4 by the upper-arm systolic BP value BP_(ASYS). Thethus determined index values API_(R), API_(L) are displayed on thedisplay device 70, as shown in FIG. 7.

[0081] Subsequently, the control device 38 judges whether themeasurement of the right-ankle BP values and/or the measurement of theleft-ankle BP values are or is abnormal.

[0082] First, at Step SB7 corresponding to the cuff-pressure regulatingmeans 80, the three switch valves 30, 46, 58 are switched to theirpressure-supply states, so that the respective air pressures P_(C1),P_(C2), P_(C3) of the three cuffs 24, 40, 52 are increased up to apredetermined pressure value sufficiently lower than the diastolic BPvalue of the patient, and then are maintained at that value.

[0083] At the following Step SB8, the control device 38 judges, based onthe pulse-wave signal SM₁ supplied from the pulse-wave filter circuit36, whether the filter circuit 36 has detected a waveform correspondingto one heartbeat-synchronous pulse of the right-posterior-tibial-arterypulse wave. If a negative judgment is made at Step SB8, the controlskips Step SB9 and proceeds with Step SB10. On the other hand, if apositive judgment is made at Step SB8, the control goes to Step SB9corresponding to the inferior-limb pulse-wave-sharpness determiningmeans 102. At Step SB9, the control device 38 determines a height, a, ofa center of gravity of an area enveloped by the waveform of the oneheartbeat-synchronous pulse wave detected at Step SB8, and additionallydetermines an amplitude, b, of the waveform of the one pulse. Based onthe thus determined height a and amplitude b, the control device 38determines a sharpness degree, %MAP(R), of theright-posterior-tibial-artery pulse wave. Step SB9 is followed by StepSB10.

[0084] At Step SB10, the control device 38 carries out an identicaloperation on the left ankle 16. That is, the control device 38 judges,based on the pulse-wave signal SM₂ supplied from the pulse-wave filtercircuit 50, whether the filter circuit 50 has detected a waveformcorresponding to one heartbeat-synchronous pulse of theleft-posterior-tibial-artery pulse wave. If a negative judgment is madeat Step SB10, the control skips Step SB11 and proceeds with Step SB12.On the other hand, if a positive judgment is made at Step SB10, thecontrol goes to Step SB11 corresponding to the inferior-limbpulse-wave-sharpness determining means 102. At Step SB11, the controldevice 38 determines a height a of a center of gravity of an areaenveloped by the waveform of the one heartbeat-synchronous pulse wavedetected at Step SB10, and additionally determines an amplitude b of thewaveform of the one pulse. Based on the thus determined height a andamplitude b, the control device 38 determines a sharpness degree,%MAP(L), of the left-posterior-tibial-artery pulse wave. Step SB11 isfollowed by Step SB12.

[0085] At Step SB12, the control device 38 carries out an identicaloperation on the upper arm 20. That is, the control device 38 judges,based on the pulse-wave signal SM₃ supplied from the pulse-wave filtercircuit 62, whether the filter circuit 62 has detected a waveformcorresponding to one heartbeat-synchronous pulse of the brachial-arterypulse wave. If a negative judgment is made at Step SB12, the controlskips Step SB13 and proceeds with Step SB14. On the other hand, if apositive judgment is made at Step SB12, the control goes to Step SB13corresponding to the superior-limb pulse-wave-sharpness determiningmeans 104. At Step SB13, the control device 38 determines a height a ofa center of gravity of an area enveloped by the waveform of the oneheartbeat-synchronous pulse wave detected at Step SB12, and additionallydetermines an amplitude b of the waveform of the one pulse. Based on thethus determined height a and amplitude b, the control device 38determines a sharpness degree, %MAP(A), of the brachial-artery pulsewave. Step SB13 is followed by Step SB14.

[0086] At Step SB14, the control device 38 judges whether the threefilter circuits 36, 50, 62 have detected respective waveformscorresponding to respective one heartbeat-synchronous pulses of theright-posterior-tibial-artery pulse wave, theleft-posterior-tibial-artery pulse wave, and the brachial-artery pulsewave. If a negative judgment is made at Step SB14, the control goes backto Step SB8 and the following steps. On the other hand, if a positivejudgment is made at Step SB14, the control goes to Step SB15corresponding to the pulse-wave displaying means 112. At Step SB15, thecontrol device 38 controls the display device 70 to display, togetherwith the right-ankle systolic BP value BP_(RSYS), the left-anklesystolic BP value BP_(LSYS), and the upper-arm systolic BP valueBP_(ASYS) displayed at Step SB4, the waveform of theright-posterior-tibial-artery pulse wave, the waveform of theleft-posterior-tibial-artery pulse wave, and the waveform of thebrachial-artery pulse wave, each along a time axis 114, as shown in FIG.7. FIG. 7 shows an example of the three BP values BP_(RSYS), BP_(LSYS),BP_(ASYS) displayed at Step SB4, the two index values API_(R), API_(L)displayed at Step SB6, and the three pulse-wave waveforms displayed atStep SB15. The display device 70 displays, alon the time axis 114, thethree pulse-wave waveforms, side by side, so that an observer cancompare those waveforms with one another.

[0087] Step SB15 is followed by Step SB16 corresponding to theBP-measurement-abnormality judging means 106. At Step SB16, the controldevice 38 judges whether the degree of sharpness %MAP (R) of theright-posterior-tibial-artery pulse wave determined at Step SB9 is notgreater than the degree of sharpness %MAP (A) of the brachial-arterypulse wave determined at Step SB13 and simultaneously the right-anklesystolic BP value BP_(RSYS) determined at Step SB4 is higher than a sumof the upper-arm systolic BP value BP_(ASYS) determined at Step SB4 andthe reference value α. If a positive judgment is made, the controldevice 38 concludes that in the BP measurement carried out for the rightankle 12, the flow of blood was not completely stopped by the pressingof the inflatable cuff 24, and therefore that the BP measurement wasabnormal. Step SB16 is followed by Step SB17 corresponding to theBP-measurement-abnormality displaying means 108. At Step SB17, thecontrol device 38 controls the display device 70 to display charactersand/or symbols indicating that the BP measurement carried out for theright ankle 12 was abnormal.

[0088] If a negative judgment is made at Step SB16, or after Step SB17,the control goes to Step SB18 corresponding to theBP-measurement-abnormality judging means 106. At Step SB18, the controldevice 38 judges whether the degree of sharpness %MAP (L) of theleft-posterior-tibial-artery pulse wave determined at Step SB11 is notgreater than the degree of sharpness %MAP (A) of the brachial-arterypulse wave determined at Step SB13 and simultaneously the left-anklesystolic BP value BP_(LSYS) determined at Step SB4 is higher than a sumof the upper-arm systolic BP value BP_(ASYS) and the reference value α.If a positive judgment is made, the control device 38 concludes that inthe BP measurement carried out for the left ankle 16, the flow of bloodwas not completely stopped by the pressing of the inflatable cuff 40,and therefore that the BP measurement was abnormal. Step SB18 isfollowed by Step SB19 corresponing to the BP-measurement-abnormalitydisplaying means 108. At Step SB19, the control device 38 controls thedisplay device 70 to display characters and/or symbols indicating thatthe BP measurement carried out for the left ankle 16 was abnormal. If anegative judgment is made at Step SB18, or after Step SB19, the controldevice 38 quits the present control routine represented by the flowchart of FIG. 6.

[0089] As is apparent from the foregoing description, in the secondembodiment, the inferior-limb pulse-wave sharpness determining means 102(Step SB9) determines the sharpness %MAP(R) of theright-posterior-tibial-artery pulse wave detected by the pulse-wavefilter circuit 36, and the BP-measurement abnormality judging means 106(Step SB16) judges that when the pulse-wave sharpness %MAP(R) determinedby the means 102 is not greater than the sharpness %MAP(A) of thebrachial-artery pulse wave and the right-ankle systolic BP valueBP_(RSYS) is higher than the upper-arm systolic BP value BP_(ASYS) by avalue not smaller than the reference value α, the BP measurement carriedout by the right-ankle BP measuring device 14 for the right ankle 12 isabnormal. Thus, an observer or an operator such as a medical staff canknow that the BP measurement carried out for the right ankle 12 has notbeen properly carried out.

[0090] In addition, in the second embodiment, the inferior-limbpulse-wave sharpness determining means 102 (Step SB11) determines thesharpness %MAP(L) of the left-posterior-tibial-artery pulse wavedetected by the pulse-wave filter circuit 50, and the BP-measurementabsnormality judging means 106 (Step SB18) judges that when thepulse-wave sharpness %MAP(L) determined by the means 102 is not greaterthan the sharpness %MAP(A) of the brachial-artery pulse wave and theleft-ankle systolic BP value BP_(LSYS) is higher than the upper-armsystolic BP value BP_(ASYS) by a value not smaller than the referencevalue α, the BP measurement carried out for the left ankle 16 isabnormal. Thus, an observer or an operator such as a medical staff canknow that the BP measurement carried out for the left ankle 16 has notbeen properly carried out.

[0091] Moreover, in the second embodiment, the display device 70simultaneously displays the right-ankle and left-ankle systolic BPvalues BP_(RSYS), BP_(LSYS) and the upper-arm systolic BP valueBP_(ASYS), and the respective waveforms of the right and leftposterior-tibial-artery pulse waves and the brachial-artery pulse wave.Therefore, in the case where the right-ankle systolic BP value BP_(RSYS)is higher than the upper-arm systolic BP value BP_(ASYS), but thewaveform of the right posterior-tibial-artery pulse wave is less sharpthan that of the brachial-artery pulse wave, an observer can judge thatthe BP measurement carried out by the right-ankle BP measuring device 14for the right ankle 12 is abnormal and, in the case where the left-anklesystolic BP value BP_(LSYS) is higher than the upper-arm systolic BPvalue BP_(ASYS), but the waveform of the left posterior-tibial-arterypulse wave is less sharp than that of the brachial-artery pulse wave,the observer can judge that the BP measurement carried out by theleft-ankle BP measuring device 18 for the left ankle 16 is abnormal.

[0092] Next, there will be described a third embodiment of the presentinvention that relates to an inferior-limb-BP measuring apparatus 120.FIG. 8 is a diagrammatic view for explaining the construction of thepresent apparatus 120. The same reference numerals as used in the firstembodiment shown in FIGS. 1 to 4 are used to designate the correspondingelements and parts of the third embodiment shown in FIGS. 8 to 11, andthe description thereof is omitted.

[0093] In short, the inferior-limb BP measuring apparatus 120 includesan inflatable cuff 24, a piping 26, a pressure sensor 28, a switch valve30, an air pump 32, a static-pressure filter circuit 34, a pulse-wavefilter circuit 36, an ECG 72, and electrodes 74 which have respectiveconstructions identical with those of the corresponding elements 24, 26,28, 30, 32, 34, 36 72, 74 employed in the first embodiment. The cuff 24is wound around a right ankle 12 of a living subject or a patient, tomeasure a right-ankle BP value of the patient. The present apparatusadditionally includes a control device 38 including a CPU 64, a ROM 66,and a RAM 68, and a display device 70.

[0094] Moreover, an input device 122 includes a keyboard (not shown)which is manually operable by an operator for inputting at least onevalue characteristic of the patient, and which produces at least onesignal, SC, representing the input at least one characteristic value andsupplies the signal SC to the control device 38. The one or morecharacteristic values may include the age, sex, height, etc. of thepatient. Those characteristic values are physical information whichinfluences a relationship between blood pressure and informationrelating to velocity of propagation of pulse wave. One or morepredetermined items are input as the one or more characteristic values.

[0095]FIG. 9 is a diagrammatic view for explaining important controlfunctions of the control device 38 of the inferior-limb-BP measuringapparatus 120.

[0096] A map selecting means 124 selects, based on the signal SCsupplied from the input device 122, one of a plurality of predeterminedmaps which correspond to a plurality of predetermined ranges for theinput characteristic value, respectively, which are stored in the ROM66, and each of which indicates, in a graph defined by a first axisrepresenting blood pressure BP and a second axis representinginformation relating to velocity of propagation of pulse wave througharterial vessel, a calcification range which is experimentallydetermined in advance and indicates that the arterial vessel has beencalcified. FIG. 10 shows an example of the maps stored in the ROM 66 andselected by the map selecting means 124. The map of FIG. 10 indicates,in a graph defined by a first axis representing systolic blood pressureBP_(SYS) and a second axis representing inverse, 1/DT, of propagationtime, DT, of pulse wave, a normal range and a calcification range. Atthe same BP value, the velocity of propagation of a pulse wave whichpropagates through a calcified artery is higher than that of a pulsewave which propagates through a non-calcified artery. That is, at thesame BP value, the inverse 1/DT of the propagation time DT of the pulsewave which propagates through the calcified artery is greater than thatof the pulse wave which propagates through the non-calcified artery.Therefore, in the map shown in FIG. 10, the calcification range islocated above the normal range.

[0097] A calcification judging means 126 judges whether the right-ankleBP value measured by the right-ankle BP determining means 82 and theright PWV-relating information obtained by the rightPWV-relating-information obtaining means 88 fall in the calcificationrange of the selected map and, if a positive judgment is made, judgesthat at least one blood vessel running in the right ankle 12 aroundwhich the cuff 24 is wound has been calcified to such a degree that theblood vessel cannot be fully or completely occluded by the pressing ofthe cuff 24, that is, the blood flow cannot be fully stopped by the cuff24.

[0098] A BP-measurement-abnormality displaying means 128 controls, ifthe calcification judging means 126 judges that the blood vesselsrunning in the right ankle 12 around which the cuff 24 is wound havebeen calcified to such a degree that the blood vessels cannot be fullyoccluded by the cuff 24, the display device 70 to display charactersand/or symbols indicating that the BP measurement carried out for theright ankle 12 is abnormal.

[0099]FIG. 11 is a flow chart representing a control program accordingto which the control device 38 of the inferior-limb-BP measuringapparatus 120 is operated.

[0100] First, at Step SC1, the control device 38 judges whether thecontrol device 38 has received, from the input device 122, the signal SCrepresenting the characteristic value of the patient, and thereby judgeswhether the characteristic value has been input by the operator.

[0101] If a negative judgment is made at Step SC1, Step SC1 is repeated.Meanwhile, if a positive judgment is made at Step SC1, the control ofthe control device 38 goes to Step SC2 corresponding to the mapselecting means 124. At Step SC2, the control device 38 selects, basedon the signal SC supplied from the input device 122, one of thepredetermined maps stored in the ROM 66.

[0102] Steps SC3 to SC11 are identical with Steps SA1 to SA9 of the flowchart, shown in FIG. 4, which is employed in the first embodiment. Thus,the present apparatus 120 measures right-ankle systolic and diastolic BPvalues BP_(RSYS), BP_(RDIA), etc., and maintains the air pressure P_(C1)of the cuff 24 at a predetermined pressing pressure value sufficientlylower than the diastolic BP value of the patient. In this state, thecontrol device 38 measures a right pulse-wave propagation time, DT_(R),needed for a pulse wave to propagate from the heart to the right ankle12.

[0103] Step SC11 is followed by Step SC12 to switch the switch valve 30to its quick-deflation position, thereby quickly decreasing the airpressure of the cuff 24.

[0104] Step SC12 is followed by Step SC13 corresponding to thecalcification judging means 126. At Step SC13, the control device 38judges whether the right-ankle systolic BP value determined at Step SC6and the right pulse-wave propagation time DT_(R) determined at Step SC11fall in the calcification range of the map selected at Step SC2.

[0105] If a negative judgment is made at Step SC13, the control device38 quits the present control routine. On the other hand, if a positivejudgment is made at Step SC13, the control of the control device 38 goesto Step SC14 corresponding to the BP-measurement-abnormality displayingmeans 128. At Step SC14, the control device 38 controls the displaydevice 70 to display characters and/or symbols indicating that the BPmeasurement carried out for the right ankle 12 is abnormal. After StepSC14, the control device 38 quits this control routine.

[0106] As is apparent from the foregoing description, in the thirdembodiment, the map selecting means 124 (Step SC2) selects, based on thecharacteristic value input through the input device 122, one of theplurality of predetermined maps each of which indicates thecalcification range in the graph defined by the first axis representingright-ankle systolic blood pressure BP_(RSYS) and the second axisrepresenting pulse-wave propagation time DT_(R). The calcificationjudging means 126 (Step SC13) judges whether the measured right-anklesystolic BP value BP_(RSYS) and the measured pulse-wave propagation timeDT_(R) fall in the calcification range of the map selected by the mapselecting means 124, and thereby judges whether the arterial vesselsrunning in the right ankle around which the cuff 24 is wound have beencalcified to such an extent that the blood flow cannot be stopped by thecuff 24. Thus, the judging means 126 judges whether the BP measurementcarried out for the right ankle 12 is abnormal.

[0107] While the present invention has been described in its preferredembodiments, it may be otherwise embodied.

[0108] For example, in the illustrated embodiment, the ECG(electrocardiograph) 72 is used as the first pulse-wave sensor commonlyfor obtaining both the right and left PWV-relating information. However,the ECG 72 may be replaced with a microphone which is worn on the chestof the living subject and detects respective heart sounds produced whenthe heart starts and ending outputting blood toward the aorta.

[0109] In addition, each first pulse-wave sensor, such as the pulse-wavefilter circuit 62 connected to the cuff 52 wound around the upper arm 20via the pressure sensor 52, may be provided by a pulse-wave sensor whichdetects a pulse wave from a portion of the subject that is more distantfrom the corresponding second pulse-wave sensor than the heart of thesubject.

[0110] Moreover, the two (right and left) first pulse-wave sensors maybe provided by two pulse-wave sensors which are adapted to be worn onrespective femoral portions of two legs of the subject.

[0111] The two (right and left) second pulse-wave sensors may beprovided by two peripheral-pulse-wave sensors which are adapted to beworn on respective one toes of two feet of the subject.

[0112] In the illustrated embodiment, each of the right-ankle BPmeasuring device 14, the left-ankle BP measuring device 18, and theupper-arm BP measuring device 22 measures a BP value according to theoscillometric method. However, each of the three BP measuring devices14, 18, 22 may be one which measures a BP value according to awell-known Korotkoff-sound method in which a BP value is measured basedon a cuff-pressure value read at a time when Korotkoff sounds are firstor last detected. Otherwise, each device 14, 18, 22 may be one whichmeasures a BP value according to a supersonic Doppler method in which,while a pressure which presses an artery is changed, a supersoundemitter and a supersound receiver which are provided right above theartery cooperate with each other to detect the opening and closing ofthe arterial vessel.

[0113] Each of the three BP measuring devices 14, 18, 22 of the firstembodiment and the upper-arm BP measuring device 22 of the secondembodiment may be provided by a BP measuring device which does notemploy any inflatable cuffs, such as an invasive BP measuring devicewhich invasively measures a BP value of a subject.

[0114] The ankle/arm BP index measuring apparatus 10, 110 is a sort ofsuperior-and-inferior-limb BP index measuring apparatus wherein an ankleis selected as an inferior limb and an upper arm is selected as asuperior limb, and the inferior-limb BP measuring apparatus 120 measuresa BP value from an ankle as an inferior limb. However, a femoral portionor a toe may be selected as an inferior limb, and a wrist or a fingermay be selected as a superior limb.

[0115] In the second embodiment, the two inferior-limb pulse-wavesensors are provided by the two pulse-wave filter circuits 36, 50,respectively, which detect the respective pulse waves from therespective portions of the two inferior limbs around which the two cuffs24, 40 are wound. However, the inferior-limb pulse-wave sensors may beworn on respective upstream-side portions of the two inferior limbs thatare located on respective upstream sides of the two cuffs 24, 40 as seenin respective directions in which arterial blood flows in the inferiorlimbs. Similarly, although in the second embodiment the superior-limbpulse wave sensor is provided by the pulse-wave filter circuit 62 whichdetects the brachial-artery pulse wave, the superior-limb pulse-wavesensor may be provided by a pulse-wave sensor which is adapted to beworn on a wrist or a finger.

[0116] In the third embodiment, the control device 38 obtainsinformation relating to velocity of propagation of pulse wave whichpropagates from the heart to the ankle 12 around which the cuff 24 iswound. However, two pulse-wave sensors may be worn on both sides of thecuff 24, and respective pulse waves detected by the two sensors may beused to obtain information relating to velocity of propagation of pulsewave. For example, in the case where a cuff is wound around an ankle ofa leg, two pulse-wave sensors may be worn on a femoral portion and a toeof the same leg, respectively, to obtain information relating tovelocity of propagation of pulse wave which propagates from the femoralportion to the toe. In the latter case, the apparatus 120 can moreaccurately judge whether the blood vessels of the body portion aroundwhich the cuff is wound have been calcified.

[0117] In the third embodiment, the apparatus 120 measures a BP valuefrom the right ankle 12. However, the apparatus may measure a BP valuefrom a left ankle.

[0118] It is to be understood that the present invention may be embodiedwith other changes, improvements, and modifications that may occur to aperson skilled in the art without departing from the scope and spirit ofthe invention defined in the appended claims.

What is claimed is:
 1. An apparatus for measuring asuperior-and-inferior-limb blood-pressure index of a living subject,comprising: a first blood-pressure measuring device which measures afirst blood pressure of a right inferior limb of the subject; a secondblood-pressure measuring device which measures a second blood pressureof a left inferior limb of the subject; a third blood-pressure measuringdevice which measures a third blood pressure of a superior limb of thesubject; a first information obtaining device which obtains firstinformation relating to a first velocity of propagation of a first pulsewave which propagates through a first route a portion of which runs inthe right inferior limb; a second information obtaining device whichobtains second information relating to a second velocity of propagationof a second pulse wave which propagates through a second route a portionof which runs in the left inferior limb; selecting means for selectingone of the measured first and second blood pressures that corresponds toone of the first and second information that relates to a lower one ofthe first and second velocities; and index determining means fordetermining the superior-and-inferior-limb blood-pressure index, basedon the selected one of the first and second blood pressures, and themeasured third blood pressure.
 2. An apparatus according to claim 1,wherein the index determining means comprises means for determining, asthe superior-and-inferior-limb blood-pressure index, a ratio of theselected one of the first and second blood pressures to the third bloodpressure, or a ratio of the third blood pressure to the selected one ofthe first and second blood pressures.
 3. An apparatus according to claim1, wherein the first information obtaining device comprises two firstpulse-wave sensors which are worn on two different first portions of theliving subject, respectively, and each of which detects the first pulsewave at a corresponding one of the two first portions, at least one ofthe two first portions belonging to the right inferior limb, and whereinthe second information obtaining device comprises two second pulse-wavesensors which are worn on two different second portions of the subject,respectively, and each of which detects the second pulse wave at acorresponding one of the two second portions, at least one of the twosecond portions belonging to the left inferior limb.
 4. An apparatusaccording to claim 3, wherein the first information obtaining devicecomprises first time determining means for determining, based onrespective times when the two first pulse-wave sensors detect the firstpulse wave, a first propagation time needed for the first pulse wave topropagate between said two different first portions of the livingsubject, and wherein the second information obtaining device comprisessecond time determining means for determining, based on respective timeswhen the two second pulse-wave sensors detect the second pulse wave, asecond propagation time needed for the second pulse wave to propagatebetween said two different second portions of the subject.
 5. Anapparatus according to claim 4, wherein the first information obtainingdevice comprises first velocity determining means for determining, basedon the determined first propagation time and a distance between the twofirst portions of the living body, the first velocity of propagation ofthe first pulse wave, and wherein the second information obtainingdevice comprises second velocity determining means for determining,based on the determined second propagation time and a distance betweenthe two second portions of the living body, the second velocity ofpropagation of the second pulse wave.
 6. An apparatus for measuring asuperior-and-inferior-limb blood-pressure index of a living subject,comprising: a first blood-pressure measuring device which includes afirst inflatable cuff adapted to be wound around an inferior limb of thesubject and which measures a first blood pressure of the inferior limb;a second blood-pressure measuring device which measures a second bloodpressure of a superior limb of the subject; a first pulse-wave sensorwhich detects a first pulse wave which propagates through a portion ofthe inferior limb that is located on an upstream side of the firstinflatable cuff; sharpness determining means for determining a degree ofsharpness of a heartbeat-synchronous pulse of the first pulse wavedetected by the first pulse-wave sensor; and judging means for judgingthat when the determined degree of sharpness is not greater than a firstreference value and the measured first blood pressure is higher than themeasured second blood pressure by a value not smaller than a secondreference value, the measurement of the first blood pressure by thefirst blood pressure measuring device is abnormal.
 7. An apparatusaccording to claim 6, wherein the second blood-pressure measuring devicecomprises a second inflatable cuff adapted to be wound around thesuperior limb of the subject, and wherein the apparatus furthercomprises a second pulse-wave sensor which detects a second pulse wavewhich propagates through a portion of the superior limb that is locatedon an upstream side of the second inflatable cuff; and reference-valuedetermining means for determining the first reference value based on thesecond pulse wave detected by the second pulse-wave sensor.
 8. Anapparatus according to claim 6, wherein the sharpness determining meanscomprises means for determining, as the degree of sharpness, apercentage, %MAP, of a height of a center of gravity of an areaenveloped by a waveform of the heartbeat-synchronous pulse of the firstpulse wave, relative to an amplitude of the waveform of said pulse. 9.An apparatus for measuring a superior-and-inferior-limb blood-pressureindex of a living subject, comprising: a first blood-pressure measuringdevice which includes an inflatable cuff adapted to be wound around aninferior limb of the subject and which measures a first blood pressureof the inferior limb; a second blood-pressure measuring device whichmeasures a second blood pressure of a superior limb of the subject; afirst pulse-wave sensor which detects a first pulse wave whichpropagates through a portion of the inferior limb that is located on anupstream side of the inflatable cuff; a second pulse-wave sensor whichdetects a second pulse wave which propagates through the superior limb;and a display device which simultaneously displays the measured firstand second blood pressures and the detected first and second pulsewaves.
 10. An apparatus according to claim 9, further comprising indexdetermining means for determining a superior-and-inferior-limbblood-pressure index of the subject, based on the measured first andsecond blood pressures, wherein the display device displays thedetermined superior-and-inferior-limb blood-pressure index, in additionto the measured first and second blood pressures and the detected firstand second pulse waves.
 11. An apparatus for measuring a blood pressureof an inferior limb of a living subject, comprising: a blood-pressuremeasuring device which includes an inflatable cuff adapted to be woundaround the inferior limb and which measures, with the cuff, the bloodpressure of the inferior limb of the subject; an input device which isoperable for inputting at least one characteristic value characteristicof the subject and which produces at least one signal representing theat least one input characteristic value; map selecting means forselecting, based on the input characteristic value, one of a pluralityof predetermined maps each of which defines, in a coordinate systemhaving a first axis representing blood pressure and a second axisrepresenting information relating to velocity of propagation of pulsewave through blood vessel, a calcification range indicatingcalcification of the blood vessel; an information obtaining device whichobtains information relating to a velocity of propagation of a pulsewave which propagates between two different portions of the subject thatinclude a portion of the inferior limb around which the inflatable cuffis wound; and judging means for judging whether the measured bloodpressure and the obtained information fall in the calcification range ofthe selected map, and thereby judging whether at least one blood vesselrunning in said portion of the inferior limb has been calcified to sucha degree that a blood flow through the blood vessel cannot be stopped bythe inflatable cuff.
 12. An apparatus according to claim 11, wherein theinput device comprises means for inputting, as the at least onecharacteristic value, at least one value selected from the groupconsisting of an age of the subject, a value corresponding to a sex ofthe subject, and a height of the subject.
 13. An apparatus according toclaim 11, further comprising a memory which stores the plurality ofpredetermined maps.
 14. An apparatus according to claim 11, wherein theinformation obtaining device comprises propagation-time measuring meansfor measuring a time needed for the pulse wave to propagate between thetwo different portions of the subject.
 15. An apparatus according toclaim 14, wherein the information obtaining device further comprisesinverse-of-propagation-time determining means for determining, as saidinformation, an inverse of the propagation time measured by thepropagation-time measuring means.